block/drbd: remove unused w_start_resync declaration

w_start_resync has been removed since
commit ac0acb9e ("drbd: use drbd_device_post_work()
in more places"), so remove it.
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Acked-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/drbd/drbd_int.h

@@ -1529,7 +1529,6 @@ extern int w_send_read_req(struct drbd_work *, int);
 extern int w_e_reissue(struct drbd_work *, int);
 extern int w_restart_disk_io(struct drbd_work *, int);
 extern int w_send_out_of_sync(struct drbd_work *, int);
-extern int w_start_resync(struct drbd_work *, int);
 
 extern void resync_timer_fn(struct timer_list *t);
 extern void start_resync_timer_fn(struct timer_list *t);